[GitHub] sruehl commented on a change in pull request #29: Opm plcentitymanager

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sruehl commented on a change in pull request #29: Opm plcentitymanager
URL: https://github.com/apache/incubator-plc4x/pull/29#discussion_r228231315
 
 

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 File path: plc4j/utils/opm/src/main/java/org/apache/plc4x/java/opm/PlcEntityManager.java
 ##########
 @@ -0,0 +1,380 @@
+/*
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you under the Apache License, Version 2.0 (the
+ "License"); you may not use this file except in compliance
+ with the License.  You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing,
+ software distributed under the License is distributed on an
+ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ KIND, either express or implied.  See the License for the
+ specific language governing permissions and limitations
+ under the License.
+ */
+
+package org.apache.plc4x.java.opm;
+
+import net.bytebuddy.ByteBuddy;
+import net.bytebuddy.implementation.MethodDelegation;
+import net.bytebuddy.implementation.bind.annotation.*;
+import org.apache.plc4x.java.PlcDriverManager;
+import org.apache.plc4x.java.api.connection.PlcConnection;
+import org.apache.plc4x.java.api.connection.PlcReader;
+import org.apache.plc4x.java.api.exceptions.PlcConnectionException;
+import org.apache.plc4x.java.api.exceptions.PlcInvalidFieldException;
+import org.apache.plc4x.java.api.exceptions.PlcRuntimeException;
+import org.apache.plc4x.java.api.messages.PlcReadRequest;
+import org.apache.plc4x.java.api.messages.PlcReadResponse;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import static net.bytebuddy.matcher.ElementMatchers.any;
+
+/**
+ * Plc4x equivalent of Jpas EntityManager for implementing Object-Plc-Mapping.
+ * This means that calls to a plc can be done by using plain POJOs with Annotations.
+ * <p>
+ * First, the necessary annotations are {@link PlcEntity} and {@link PlcField}.
+ * For a class to be usable as PlcEntity it needs
+ * <ul>
+ * <li>be non-final (as proxiing has to be used in case of {@link #connect(Class)}</li>
+ * <li>a public no args constructor for instanciation</li>
+ * <li>Needs to be annotated with {@link PlcEntity} and has a valid value which is the connection string</li>
+ * </ul>
+ * <p>
+ * Basically, the {@link PlcEntityManager} has to operation "modes" represented by the methods {@link #read(Class)} and
+ * {@link #connect(Class)}.
+ * <p>
+ * For a field to get Values from the Plc Injected it needs to be annotated with the {@link PlcField} annotation.
+ * The value has to be the plc fields string (which is inserted in the {@link PlcReadRequest}).
+ * The connection string is taken from the value of the {@link PlcEntity} annotation on the class.
+ * <p>
+ * The {@link #read(Class)} method has no direkt equivalent in JPA (as far as I know) as it only returns a "detached"
+ * entity. This means it fetches all values from the plc that are annotated wiht the {@link PlcField} annotations.
+ * <p>
+ * The {@link #connect(Class)} method is more JPA-like as it returns a "connected" entity. This means, that each
+ * time one of the getters on the returned entity is called a call is made to the plc (and the field value is changed
+ * for this specific field).
+ * Furthermore, if a method which is no getter is called, then all {@link PlcField}s are refreshed before doing the call.
+ * Thus, all operations on fields that are annotated with {@link PlcField} are always done against the "live" values
+ * from the PLC.
+ * <p>
+ * // TODO Add detach method
+ */
+public class PlcEntityManager {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(PlcEntityManager.class);
+
+    private final PlcDriverManager driverManager;
+
+    public PlcEntityManager() {
+        this.driverManager = new PlcDriverManager();
+    }
+
+    public PlcEntityManager(PlcDriverManager driverManager) {
+        this.driverManager = driverManager;
+    }
+
+    public <T> T read(Class<T> clazz) throws OPMException {
+        PlcEntity annotation = getPlcEntityAndCheckPreconditions(clazz);
+        String source = annotation.value();
+
+        try (PlcConnection connection = driverManager.getConnection(source)) {
+
+            if (!connection.getReader().isPresent()) {
+                throw new OPMException("Unable to get Reader for connection with url '" + source + "'");
+            }
+
+            PlcReader reader = connection.getReader().get();
+
+            PlcReadRequest.Builder requestBuilder = reader.readRequestBuilder();
+
+            // Do the necessary queries for all fields
+            // HashMap<ReadRequestItem<?>, Field> requestItems = new HashMap<>();
+            for (Field field : clazz.getDeclaredFields()) {
+                PlcField fieldAnnotation = field.getAnnotation(PlcField.class);
+                if (fieldAnnotation == null) {
+                    // Ignore that field
+                    continue;
+                }
+                // Create the suitable Request
+                String query = fieldAnnotation.value();
+                requestBuilder.addItem(field.getName(), query);
+            }
+
+            // Build the request
+            PlcReadRequest request;
+            try {
+                request = requestBuilder.build();
+            } catch (PlcInvalidFieldException e) {
+                throw new OPMException("Unable to parse one field request", e);
+            }
+
+            // Perform the request
+            PlcReadResponse<?> response;
+            try {
+                // TODO: make configurable.
+                response = reader.read(request).get(1_000, TimeUnit.MILLISECONDS);
+            } catch (InterruptedException | ExecutionException e) {
+                throw new OPMException("Request fetching not able", e);
+            } catch (TimeoutException e) {
+                throw new OPMException("Timeout during fetching values", e);
+            }
+
+            // Construct the Object
+            T instance = clazz.getConstructor().newInstance();
+
+            // Fill all requested fields
+            for (String fieldName : response.getFieldNames()) {
+                setField(clazz, instance, response, fieldName);
+            }
+            return instance;
+        } catch (PlcConnectionException e) {
+            throw new OPMException("Unable to get connection with url '" + source + "'", e);
+        } catch (Exception e) {
+            throw new OPMException("Unable to fetch PlcEntity " + clazz.getName(), e);
+        }
+    }
+
+    /**
+     * Returns a connected proxy.
+     *
+     * @param clazz clazz to be connected.
+     * @param <T>   type of param {@code clazz}.
+     * @return a connected entity.
+     * @throws OPMException when proxy can't be build.
+     */
+    public <T> T connect(Class<T> clazz) throws OPMException {
+        getPlcEntityAndCheckPreconditions(clazz);
+        try {
+            // Use Byte Buddy to generate a subclassed proxy that delegates all PlcField Methods
+            // to the intercept method
+            return new ByteBuddy()
+                .subclass(clazz)
+                .method(any()).intercept(MethodDelegation.to(this))
+                .make()
+                .load(Thread.currentThread().getContextClassLoader())
+                .getLoaded()
+                .getConstructor()
+                .newInstance();
+        } catch (NoSuchMethodException | InvocationTargetException | InstantiationException | IllegalAccessException e) {
+            throw new OPMException("Unable to instantiate Proxy", e);
+        }
+    }
+
+    private <T> PlcEntity getPlcEntityAndCheckPreconditions(Class<T> clazz) {
+        PlcEntity annotation = clazz.getAnnotation(PlcEntity.class);
+        if (annotation == null) {
+            throw new IllegalArgumentException("Given Class is no Plc Entity, i.e., not annotated with @PlcEntity");
+        }
+        // Check if default constructor exists
+        try {
+            clazz.getConstructor();
+        } catch (NoSuchMethodException e) {
+            throw new IllegalArgumentException("Cannot use PlcEntity without default constructor", e);
+        }
+        return annotation;
+    }
+
+    //------------------------------------------------------------------------------------------------
+    //
+    //  Methods for interception for the proxy object
+    //
+    //------------------------------------------------------------------------------------------------
+
+    /**
+     * Basic Intersector for all methods on the proxy object.
+     * It checks if the invoked method is a getter and if so, only retrieves the requested field, forwarding to
+     * the {@link #fetchValueForGetter(Object, Method)} method.
+     * <p>
+     * If the field is no getter, then all fields are refreshed by calling {@link #refetchAllFields(Object)}
+     * and then, the method is invoked.
+     *
+     * @param o    Object to intercept
+     * @param m    Method that was intercepted
+     * @param c    Callable to call the method after fetching the values
+     * @param that Reference to the proxy object
+     * @return possible result of the original methods invocation
+     * @throws OPMException Problems with plc / proxying
+     */
+    @RuntimeType
+    // TODO: avoid using single letter params.
+    public Object intercept(@This Object o, @Origin Method m, @SuperCall Callable<?> c, @Super Object that) throws OPMException {
+        LOGGER.trace("Invoked method {} on connected PlcEntity {}", m.getName(), that);
+
+        if (m.getName().startsWith("get")) {
 
 Review comment:
   maybe we should assert that no method starting with get and having attributes get picked up

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